Stress increases addictive behaviors such as behavioral sensitization. Although it has been well documented that the ventral tegmental area (VTA) is the brain region whose activation is essential to induce behavioral sensitization, the mechanism through which stress increases behavioral sensitization is unknown. The main goal of this proposal is to elucidate the mechanism through which the corticotropin releasing factor (CRF) mediates NMDA receptor function and behavioral sensitization. Our preliminary data provide the first evidence for a direct synaptic modulation by CRF of synaptic transmission on a subclass of VTA dopamine (DA) neurons. Specifically, our data show that CRF activates CRF 2 receptors (CRF2R), which in combination with the CRF binding-protein (CRF-BP) increases NMDA currents in the VTA. Further, our data show that the CRF-dependent increase of NMDA currents in the VTA depends on the activation of phospholipase C (PLC) and PKC. We hypothesize that the potentiation of NMDA currents by CRF and the CRF-BP represents a key cellular phenomenon underlying stress-induced sensitization to cocaine. In specific aim 1, we want to characterize in detail the anatomical projections of the subset of DA neurons that are sensitive to CRF. Specific aim 2 will define the intracellular pathway activated by PLC that is responsible for the CRF-dependent increase of NMDA currents. Finally, specific aim 3 will study the role of CRF and of CRF2R agonists and antagonists in modulating context-dependent behavioral sensitization and stress-dependent behavioral sensitization to cocaine.